Iron-molybdenum titanium base alloys



Patented Oct. 12, 1954 IRON-MOLYBDENUM TITANIUM BASE ALLOYS Y Schuyler A. Herres and Thomas K. Redden, Las Vegas, Nev., assignors to Allegheny Ludlum Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania No Drawing. Application April 12, 1951,

Serial No. 220,722

7 Claims. 1

This invention relates to new and improved titanium-base alloys containing iron and molybdenum and a hardening element of the type of oxygen and nitrogen. These alloys are suitable for more critical utilizations requiring an improved tensile and yield strength, a good ductility for cold working, an excellent corrosion resistance and which may be reversibly hardened and softened by heat treatment. This application is a continuation-in-part of our application, Serial No. 118,723, entitled Titanium Alloys, filed Septcmber 29, 1949.

Alloys of the type with which we are here concerned are suitable for structural uses where higher strength and lighter weight are essential such as in aircraft and turbine utilizations.

--An object of our invention has been to provide new and improved titanium-base alloys containing iron and molybdenum metal alloying elements and gaseous alloying elements of the class of nitrogen and oxygen.

The constituents of these alloys fall within the following critical ranges:

TABLE I 02:0.02 to 0.40% Fe=0.5 to 3.0% Mo=1.0 to 5.0%

N2=0.05 to 0.25% Fe=0.5 to 3.0% Mo=1.0'to 5.0%

02:0.02 to 0.40% N2=0.02 to 0.30% Fe=0.5 to 3.0% M=1.0 to 5.0%

Balance titanium in each of A, B and C.

For optimum results in alloy A, the iron should be a minimum of about 25 times the oxygen content and not substantially less than about of the, molybdenum content. The oxygen is used Within the permissible range and is proportioned to the molybdenum and iron to provide hardening without excessive hardness.

For optimum results in alloy B, the iron should be a minimum of about times the nitrogen content and not substantially less than about of the molybdenum content. The nitrogen is used within the permissible range and is proportioned to the molybdenum and iron to provide hardness without excessive hardness.

In alloy 0 where both nitrogen and oxygen are used, their ranges are substantially the same, except that the range of nitrogen is slightly greater than where it is used separately, as in alloy B.

2 The lower and upper limits of the iron and molybdenum are the same as before and the ratios are substantially the same.

The following table sets forth alloys within the ranges of Table I, giving tensile properties and hardness for representative optimum alloys:

TABLE II Titaninl m base alloys containing iron and molybdenum and oxygen or nitrogen Composition (Balance Ti) Tensile Percent R. A., BHN Strength Elong. Percent 02 N2 Fe M0 The alloys set forth in the Table II were made by tungsten-arc melting in a water cooled copper crucible under an argon atmosphere. These alloys were subjected to the normal heat treatment hereinafter set forth, followed by air cooling.

TABLE III Quench hardening A. Composition:

N2 Fe I 1.6 Mo 2.4 Balance titanium Vickers Quenching Temperature Hargness Samples were quenched in cold water from the above temperatures.

These alloys are capable of being hardened by rapid cooling from above about 1300 F. After hardening, they may be softened by holdingat temperatures below.1300 F. and slow .cooling.

The normal heat treatment involves hot working them within an optimum range of about 1400" to 1'l00 F. and annealing at about 1300" F. after working. Generally speaking, hot working within a temperature range of about l400 to l800 F., followed by cooling in air produces desirable properties for most structural uses. A subsequent anneal or stress relief (solution treatment) is preferred to obtain uniformity of properties. This is accomplished by reheating to a temperature within the range of about 1200 to 1600 F. and cooling at a suitable rate. Alloys B and respond favorably to heat treatment and may be hardened by rapid cooling, as water quenching from temperatures above about 1500 F., or softened by relatively slow cooling from the same temperature.

Form-molybdenum is used in making these alloys (may be composed of about 60% molybdenum and 40% iron) to carry out the novel procedure set forth in our copending application Serial No. 118,723, abovementioned.

All the alloys may also be hardened by an age hardening treatment on holding attemperatures within a range of 400 to 1000 F. for a length of time depending upon the temperature employed, see Tables IV and V.

4 depend upon the degree of cold work accomplished.

All the alloys may be surface hardened by heating in air or atmospheres, mixtures, or fused baths that provide nitrogen or oxygen or both for combination with the titanium. For example, titanium heated in the presence of oxygen for about one hour at 1900 F. is hardened for a depth of about .050 of an inch below the surface with a maximum surface hardness of 400 Brinell. Similar surface hardening effects are produced by heating titanium or the alloys in a nitrogenrich atmosphere, such as ammonia gas at temperatures as low as 950 F. The depth and degree of hardness produced is controlled by time and temperature of exposure as well as the composition of the atmosphere or bath used.

In accordance with our procedure, ferrous metal, and particularly a ferrous combination of molybdenum, is added to the titanium while it is in a molten state and an ambient atmosphere is maintained that is non-contaminating of the titanium. The oxygen or nitrogen may be added in controlled amounts by introduction of the gas or gases to the furnace during melting or by additions as com-pounds of oxygen or nitrogen with titanium.

What we claim is:

TABLE IV 1. A titanium-base alloy consisting of .10 to 30 .40-% oxygen, about .8 to 3% iron, about 1.2 to %9 Pep Pep 4.5% molybdenum, and the remainder titanium. Heat Treatment g ffi i cent cent .2. A titanium-base alloy consisting of .12 "to 02 Fe Mn Ekmg- 27% nitrogen, about 1.6 to 2% iron, about 2.4 V to 3% molybdenum, and the remainder tita 0.1 3.0 4.5 143 hrs. at 600 178,100 9 n 1 3 0 4 5 13 OF Mr 142 15 .31 3. A titamum-base alloy consisting essentially 1: :4 1a3 at 506 5:1 5 10 Of at least 'QnB alloying gas range R o specified of: .02 to .40% oxygen and .05 to 25% 12 t 5* 11588 tyfifiif- 23238 1% 2?, nitrogen, about .5 to 3% iron, about 1 to 5% mo- 2 3 at 173,600 6 40 lybdenum, and the remainder titanium; the g alloy being characterized by its improved tensile and yield strengths with adequate ductility, cor- TABLEV rosion resistance, and ability to be reversibly Composition: hardened and softened by temperature treat- Percent ment. O2 0.1 4. A titanium-base alloy as defined in claim 3 Mo 2.4 wherein the iron content is a minimum of about Fe 1:6 25 times its oxygen content and a minimum of Rockwell A hardness after heat treatment samples quenched from 1300 F. in water and given following treatment 400 )3. 000 F. 800 F. 1,000 F. 1,200 F.

Hours ..2 1e s0 2 16 2i16' 50 2 1s 50 2 1e 50 "6163.5 61 65.5 63.5 65' 62.5 52.5 59 sea 60. 59.5 60.5. 60.5

All the alloys are also capable of being hardened, following rapid cooling from a temperature above about 1200 F., by an aging and precipitation hardening mechanism on reheating and holding for various periods within a temperature range of about 700 to 1200 F. The time of holding is .less, thehigher the aging temperature in this range and the effect isreversible, so that the alloy may again be softened by reheating to a high temperature. The alloys may also be hardened by :cold working, .i. e., mechanical reduction in cross-sectional area at temperatures below about 1200 F., and may be softened again by heating to a temperature above about 1200 F. and slowly cooling. The temperature and the time employed in the softening operation will about 10 times its nitrogen content and is not substantially less than about one-half of the molybdenum content.

5. A titanium-base alloy consisting of .02 to .40% oxygen, about .5 to 3% iron, about 1 to 5% molybdenum, and the remainder titanium; the iron content being a minimum of about 25 times the oxygen content and being not substantially less than one-half of the molybdenum content.

'6. A titanium-base a'lloy consisting of .05 to 25% nitrogen, about .5 to 3% iron, about 1 to 5% molybdenum, and the remainder titanium; the iron content being a minimum of about 10 times the :nitrogen content and not substantially less than about one-half of the molybdenum content.

7. A titanium-base alloy consisting essentially of .02 to .40% oxygen, .02 to 30% nitrogen, about .5 to 3% iron, about 1 to 5% molybdenum, and the remainder titanium; the alloy being characterized by its improved tensile and yield strengths with adequate ductility, corrosion resistance, and the ability to be reversibly hardened and softened by temperature treatment.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,188,765 Young Jan. 30, 1940 2,258,992 Mansfield Oct. 14, 1941 2,294,648 Ansel et al. Sept. 1, 1942 2,467,367 Austin Apr. 19, 1949 6 Number Name Date 2,497,667 Gresham et a1. Feb. 14, 1950 2,520,753 Ball et a1. Aug. 29, 1950 2,554,031 Jaifee et a1 May 22, 1951 2,575,962 Jaffee et a1 Nov. 20, 1951 2,588,007 Jafiee Mar. 4, 1952 FOREIGN PATENTS Number Country Date 718,822 Germany Mar. 24, 1942 OTHER REFERENCES AF Technical Report No. 6218, Part 2, Research and Development on Ti Alloys, published 1950 by Battelle Memorial Institute, page 66.

Metallurgia, June 1949, page 72. 

3. TITANIUM-BASED ALLOY CONSISTING ESSENTIALLY OF AT LEAST ONE ALLOYING GAS WITHIN THE RANGE SPECIFIED OF: .02 TO .40% OXYGEN AND .05 TO .25% NITROGEN, ABOUT .5 TO 3% IRON, ABOUT 1 TO 5% MOLYBDINIUM, AND THE REMAINDER TITANIUM; THE ALLOY BEING CHARACTERIZED BY ITS IMPROVED TENSILE AND YIELD STRENGTHS WITH ADEQUATE DUCTILITY CORROSION RESISTANCE, AND ABILITY TO BE REVERSIBLY HARDENED AND SOFTENED BY TEMPERATURE TREATMENT. 